Coplanar Printed Balun Using Coupling Microstrip Group
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Solution Overview
Problem
Existing baluns, such as low-temperature co-fired ceramic baluns, are bulky and expensive, making it challenging to design a compact and cost-effective solution for transforming unbalanced broadcasting signals into balanced signals in communication apparatuses.
Innovation Solution
A balun is printed on a substrate with a coupling microstrip group and input/output ports arranged coplanarly, utilizing a ground layer and clearance area to transform unbalanced signals into balanced signals, with an input matching circuit and distributed coupling lines for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low-temperature co-fired ceramic balun is used, then the balun can transform unbalanced signals into balanced signals, but the balun becomes bulky and expensive
Solution Approach 1:
The patent replaces the traditional mechanical low-temperature co-fired ceramic balun structure with a printed circuit board-based balun using microstrip lines. The coupling microstrip group (30) with distributed coupling sections (318, 319) and coupling lines (33, 36) transforms the mechanical ceramic structure into a planar printed circuit implementation, achieving signal transformation while reducing size and cost
Solution Approach 2:
The patent transitions from a three-dimensional ceramic balun to a two-dimensional planar structure printed on the substrate surface. The coupling microstrip group and input/output ports are arranged coplanarly on the first surface (101) of the substrate, utilizing the planar dimension to achieve compact integration while maintaining signal transformation functionality
2Reliability
If a low-temperature co-fired ceramic balun is used, then the balun can transform unbalanced signals into balanced signals, but the balun becomes expensive
Solution Approach 1:
The patent replaces the expensive ceramic manufacturing process with standard printed circuit board fabrication techniques. The coupling microstrip group (30) with its coupling sections (318, 319) and coupling lines (33, 36) is implemented using conventional PCB trace patterns, ground layers (70), and clearance areas (80), leveraging existing manufacturing infrastructure to reduce costs
Solution Approach 2:
The patent integrates multiple functions into a single printed circuit board structure. The substrate (10) with its ground layer (70), clearance area (80), coupling microstrip group (30), and input/output ports (20, 40, 50) simultaneously provides signal transformation, grounding, isolation, and structural support, eliminating the need for separate ceramic components and reducing overall manufacturing complexity
3Volume of moving object
If the input port, coupling microstrip group, and output ports are arranged coplanarly on the substrate, then the balun achieves compact size, but the signal transformation performance must be maintained
Solution Approach 1:
The patent utilizes the planar surface of the substrate to arrange all components (input port 20, coupling microstrip group 30, output ports 40, 50) coplanarly on the first surface (101). This two-dimensional arrangement achieves compact integration while the distributed coupling sections (318, 319) and coupling lines (33, 36) maintain signal transformation through controlled electromagnetic coupling in the planar domain
Solution Approach 2:
The patent divides the coupling microstrip group (30) into multiple coupling sections (318, 319) with connecting sections (314) and multiple coupling lines (33, 36). This segmentation allows distributed coupling along the signal path, maintaining transformation performance while enabling compact coplanar arrangement on the substrate surface
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution results in a compact, low-cost balun with effective signal transformation, achieving input return loss below -20 dB and insertion losses greater than -5 dB across 0.95 GHz-2.15 GHz, maintaining phase balance and providing balanced signals.
Implementation Method 1
The coupling microstrip group 30 is connected between the input port 20 and the first and second output ports 40 and 50 to transform the unbalanced signal into the first and second balanced signals
Data Source
AI summary
A balun includes an input port, a first output port, a second output port and a coupling microstrip group including an input line connected to the input port, a first output line connected to the first output port, a first coupling line, a second output line connected to the second output port and a second coupling line. The input line includes a first coupling section connected to the input port, a second coupling section opposite to the first coupling section and a connecting section connected between the first coupling section and the second coupling section. An unbalanced signal is transformed into a first balanced signal via coupling among the first coupling section, the first output line and the first coupling line. An unbalanced signal is transformed into a second balanced signal via coupling among the second coupling section, the second output line and the second coupling line.